This invention relates to a corrosion-resistant apparatus for processing substrates in a plasma, and in particular, to the processing of semiconductor wafers.
An ionized gas or "plasma" is used in many types of manufacturing processes, including for example, in semiconductor manufacturing processes. For example, a plasma can be used for cleaning semiconductor processing chambers, as described in U.S. Pat. No. 5,201,990, to Chang, et al., which is incorporated herein by this reference. A plasma is also used in plasma-enhanced chemical vapor deposition (CVD) processes for depositing coatings onto substrates, as described in U.S. Pat. No. 5,093,150, to Somero, et al., and U.S. Pat. No. 4,969,415, to Bartha, et al., both of which are incorporated herein by this reference. Another example is the use of plasma in reactive ion-etching processes to etch through metallic layers on substrates, as for example, described in U.S. Pat. No. 4,190,488, to Winters, and in U.S. Pat. No. 4,468,285, to Bayman, both of which are incorporated herein by this reference.
Plasma processing is generally carried out in an enclosed metal processing chamber containing metallic components. The metal components are used for loading and positioning substrates into the chamber, and for controlling process gas flow into and out of the chamber. The components are generally fabricated from metals and alloys such as stainless steel, aluminum, "INCONEL", "HAYNES", and "HASTALLOY". These materials can corrode in a plasma environment, particularly when the plasma is generated from a reactive gas. For example, the fluorine ions of the plasma of nitrogen trifluoride (which is used to clean processing chambers), is highly corrosive and readily corrodes metal components.
Corrosion of the metal components limits the life of the processing apparatus, consequently increasing the down time of the apparatus, and the cost of processing the semiconductor substrates. Also, corroded components can flake and create contaminant particles in the processing chamber, which can deposit on the substrate. It is difficult to non-destructively detect such contamination during the initial stages of fabricating the integrated circuit. Thus, it is only in the final stages of the manufacturing process, when the fully processed semiconductor substrates are worth between $50,000 to $100,000 each, that the contaminant deposits are discovered, and the entire wafer must be scrapped.
Thus, there is a need for metal structures, such as plasma processing apparatus, that resist corrosion when exposed to corrosive plasma environments, and which have reduced production of particles resulting from corrosion.